Qual é a diferença entre ι e η ?Você pode indicar exemplo de resposta.

There isn't any specific rule to know when to use one over the other which means that you have to remember how each word is written by heart. However, there are a few instances where you'll be able to tell with certainty which one you have to use:

When a neuter noun ends with the sound "ee" it will most likely be a "ι" eg: το παιδί, το σκοινί, το σπίτι etc.

When a feminine noun ends with the sound "ee" then it will be an "η" eg: η γιορτή, η εποχή, η βροχή etc.

There are more rules like these ones that you'll find out as you start learning more advanced grammar but it's important to know that, most of the time, you just have to know how the word is written in order to be able to write it correctly.